1. Field of the Invention
The present invention is for an ophthalmic instrument, and more particularly, pertains to an eye positioner which can be utilized for positioning, manipulating, and fixating the eye during opthalmology surgery, eye exams, refractive surgery, and laser treatment. It can be used in various types of refractive surgery such as PRK, LASIK, Holmium: YAG Thermokeratoplasty, various ophthalmic laser treatments such as YAG, femto second laser, dye laser, photocoagulation using various laser wavelengths, intracorneal ring insertion and removal, incisional keratotomy, ophthalmic exams, corneal surgery, and foreign body removal.
2. Description of the Prior Art
Prior art eye fixation hand pieces are used by surgeons for engaging and holding an eye at a fixed reference position during eye surgery. Some of these hand pieces, such as the Thornton fixation ring, engage the eye with teeth or serrated edges. Others, such as the one shown in Krasner, U.S. Pat. No. 4,796,623, suggest a vacuum attachment to the eye, but painfully deform the eye between ridges. Vacuum attachment of an eye fixation device is also suggested in FIG. 2 of L'Esperance, U.S. Pat. No. 4,718,418, and in O'Dell, U.S. Pat. No. 4,558,698; but these are not hand pieces.
One device that has been proposed for use in fixating the eye of a patient is shown in Clapham, U.S. Pat. No. 5,009,660. The Clapham device utilizes a vacuum ring and purging gas system at the end of a handle which extends away from the vacuum ring handle at an angle. The vacuum ring can be secured to the eye around the cornea. The purging system is for dispersing evaporated tissue. A gas purging eye fixation hand piece includes a vacuum ring evacuated by a suction line through a handle via connection to a vacuum pump, by which a purging gas is delivered to an array of purging nozzles aimed into the vacuum ring from around an inner perimeter of the vacuum ring to direct purging gas jets toward the proximal side of the vacuum ring attached to an eye that is held steady in a reference position for laser surgery. A preferably disposable and resilient eye-engaging ring is removably mounted on the vacuum ring to engage the eye around the cornea, and a spring-biased suction release valve is preferably mounted on the hand piece handle for finger operation by the surgeon to release the hand piece from the eye when surgery is completed. Mounting of gas purging nozzles on the hand piece automatically positions them properly for keeping the cornea clear of particles formed by laser ablation of eye tissue, once the hand piece is properly fixed to the eye.
L'Esperance, U.S. Pat. No. 4,718,418, uses a vacuum ring which can be placed on the eye, but the vacuum ring is rigidly connected to an external piece of equipment (in this case, a laser used in treatment of the eye). This technique has inherent dangers, however, in that if the patient should panic or for whatever reason attempt to move away from the rigid device, serious trauma to the eye can result.
Eye Fixation Speculum, U.S. Pat. No. 5,171,254, describes an ophthalmic instrument for fixating a patient's eye during an ophthalmic procedure. The instrument includes a speculum securable against the patient's bony orbit, and a fixation ring attachable to the patient's eye, the ring including both a mechanism for fixating the ring with respect to the eye and a mechanism for adjustably attaching the ring to the speculum. The instrument may include one or more bubble-type levels carried on the fixation ring for indicating the orientation of the ring and assisting the surgeon in orienting the eye of the patient before securing the ring to the speculum. Other devices are used with incisional devices attached to vacuum rings for RK (radial keratotomy) and with trephines, all having tubing and external vacuum sources.
Currently, ophthalmologists often merely use a pair of forceps or a metal ring to stabilize the eye during such procedures. Obviously, this can be less than satisfactory, as it can be difficult to get a secure grip on the eyeball. Squeezing the eye with the forceps can elevate intraocular pressure and deform the shape of the cornea, inducing astigmatism. The most frequently used method is to ask the patient to keep his eye immobilized by fixating on an illuminated target. This is very difficult for most patients during excimer laser surgery, especially when the eyelids are being held open by a speculum and distracting noises are produced by the high energy laser striking the cornea. In radial keratotomy (RK), it is extremely important for the patient to hold the eye absolutely still when the multiple incisions of the cornea are made with the diamond scalpel or serious complications could occur. The other available fixation method is to use a pair of forceps (similar to tweezers) and firmly grasp the white portion of the eye. This is also an unsatisfactory method which causes pain for the patient and distorts the eye.
The Thornton ring consists of either a partial or complete circular ring with a series of teeth for gripping the eye at the sclera (white area) and a handle protruding at an angle from the ring. The instrument, due to the ring teeth, is painful for the patient because the anesthetic is only effective for the cornea and does not completely penetrate and anesthetize the sclera.
Forceps, a tweezers-type instrument, are also painful as they are used to grasp the eye at the sclera by pinching, which often causes a hemorrhage. The cornea shape easily becomes distorted, inducing astigmatism, and the intraocular pressure rises unpredictably. Forceps have a numbers of drawbacks including subconjunctival hemorrhage and pain which can cause increased patient anxiety. Disadvantages can include torsion movements when a patient tries to move an eye with one point fixation and the resultant movement is incyclo or excyclotorsion. Depending on the degree of pressure exerted by the surgeon, the intraocular pressure can fluctuate greatly. In RK, the depth of each incision may vary depending on the intraocular pressure, and surgeons will try to maintain a constant intraocular pressure by altering the forceps pressure on the eye. Corneal distortion also occurs depending on the force exerted and distance from the cornea of the forceps. It is not completely understood how altering the corneal shape intraoperatively during RK, LASIK and PRK affects the outcome. The use of various rings with multiple small teeth, such as the Thornton ring, eliminates some of the problems with one-point fixation. However, all these methods have several drawbacks.
Some prior art devices, including ring structures and a tubular component connected thereto, were problematic in that the connection between the ring structures and the tubular component was of secondary consideration and of barely adequate construction. Often, the connection therebetween was not entirely suitable with respect to a solid pressure or vacuum connection, or the stability of the ring structures with respect to the tubular component was not entirely satisfactory. The present invention provides an eye positioner which provides for excellent pressure or vacuum connections and which provides for suitable accommodation and connection of a tubular component to the ring structure by the use of the attachment fixture.
Some prior art devices included ring structures formed of a rigid support ring having an annular channel which accommodated a flexible sealing ring affixed therein by frictional engagement, adhesive, or a combination thereof. As such, the attachment of the rigid support ring to the flexible sealing ring may have been of secondary consideration. Such connections were not entirely suitable, particularly when an adhesive bond may not have been evenly applied, resulting in nonlinear geometry, irregular structure, and the like. The present invention overcomes the inadequacies of the prior art by providing an annular vacuum ring in which a flexible sealing ring is overmolded onto a channeled support ring.
The invention also ensures that any modest change in the intraocular pressure of the eye is both controlled and predictable, unlike the prior art methods (such as grasping the eye with a forceps) which can induce erratic changes in intraocular pressure and concomitant distortion of the corneal topography.
The instrument of the invention also eliminates the problems encountered due to patient eye movement during exams and ophthalmic surgery.